The objective of this work is to characterize in mechanistic detail the way by which certain hydrolytic enzymes function. Information obtained from these studies could contribute to the development of improved methods for treating and characterizing certain metabolic diseases in man which arise from an abnormality in a hydrolytic enzyme. The ionization behavior of groups at the active site of papain will be studied using pmr spectroscopy, and reporter groups fixed to the active-site thiol group of papain. The ionization and catalytic behavior of low molecular wt. model compounds will be studied, in order to establish the reason for the unusual properties of the groups at the active site of papain. The kinetics of loss of an alpha-deuterium atom in substrates of D-serine dehydratase will be determined, in order to characterize further the relative rates of individual steps in the catalytic pathway. The usefulness of apo-D-serine dehydratase as a convenient clinical assay tool for determining the role of pyridoxal 5'-phosphate in human disease states, will be assessed.